If you want your web pages to be even considered for ranking on Google, you need backlinks. Without them, there is virtually no way of making it to the top of search engine result pages (SERPs).
Still, you will find some claiming to rank their websites without any backlinks. Problem with that is you probably cannot replicate the same steps for your niche, especially if it is a highly competitive one.
That is exactly why there is a third pillar of search engine optimization (SEO). Off-page SEO, aka linkbuilding, is how you can secure (and almost guarantee) high rankings on the SERPs.
Over the years, SEOs have come up with more than hundred ways of getting backlinks. Some work, some don’t, and some ruin your website’s ranking.
Google punishes some of these techniques, warns against a lot of them, and does not like any of them.